A battery monitor executes a voltage measurement mode and a sleep mode alternately to reduce power consumption of a secondary battery.
While the secondary battery is used, the battery monitor that monitors the secondary battery usually receives an actuation signal from a load side and is actuated to be switched from the sleep mode to the voltage measurement mode. Therefore, the battery monitor continuously monitors the state of the secondary battery while the secondary battery is used.
However, if the secondary battery is separated from the load to be used or an error or a problem occurs in the communication between the secondary battery and the load, the battery monitor cannot receive the actuation signal from the load side. There has been no consideration for dealing with such a case. This kind of problem occurs in other elements than the secondary battery, for example, capacitors.